Method of reconditioning metal



March 26, 1940. oss ET 2,194,909

METHOD OF RECONDITIONING METAL Filed Nov. 29, 1955 v INVENTORS H flspamr Mass.

' BZJSEPH A? DAWSON.

ATTORNEY Patented Mar. 26, 1940 UNITED STATES PATENT OFFICE METHOD or lmcolvnirromo METAL jApplication November as, 1933, Serial No. 700,188

3 Claims. (01. 14 8-21.5)

This invention relates to a method of eliminating certain objectionable metallurgical changes which are produced in high carbon and alloy steels when they are severed by means of high temperature heating and oxidizing agents, e. g., the oxy-acetylene cutting flame.

By the operation of high temperature or flame cutting, surfaces and surface edges of certain grades of steel are hardened or otherwise altered 10 team extent which renders the flame cut surfaces and surface edges too hard or otherwise unsuited to withstand the commercial operations of fabrication and erection, and subsequentservicein industry and commerce. This hardening or other 15 change in the desirable physical propertiesof these steels invites the formation of fine hair cracks or ruptures in the steel at the cut surfaces and surface edges which serve as roots, such as sharply defined notches, for immediate. or subsequent 26 cracking. This characteristic is particularly true of those grades of steel (such as carbon steels containing above about 0.35% carbon, the structural silicon steels and some steel alloys containing nickel, chromium, manganese or vanadlum) of which the compositions are such as to impart to them the property of 'air hardening when they are heated beyond their recrystallization temperature and allowed to cool freely in air, conditions which are approached or duplicated in the severing of such metals by the ordinary practices of flame cutting. Furthermore, it is very difficult and expensive to machine such hardened surfaces by customary machine tools,

as for example, in removing the hardened metal 35 or in milling the ends of structural steel members which have been rough sized by flame cutting. Consequently these disadvantages have impeded the use of flame cutting for such steels.

Accordingly, the principal object of this invention is to provide an improved method of reconditioning or restoring the metallurgical structure of such severed steel surfaces to reestablish therein the desirable properties of the metal so that it may be used directly for struc- 43 tural purposes without machining off hardened edges and without the customary furnace heat treatment of the'entire piece of steel.

The above and other objects, as well as the novel features of this invention, will become more apparent from the following description considered in connection with the accompanying drawing, in which: i

. Figs, 1, rand 3 are respectively side, end and plan views 'of a machine embodying this inven- "1, 2 and 3.

tion and adapted for use in practicing the improved method; and

Fig. 4 is a plan view showing an alternative form of the blowpipe B appearing in Figures Ordinarily when the oxy-acetylene cutting 5 flame (consisting of one or more high temperature gaseous heating jets and a gaseous oxidizing jet) progressively severs metal such as a plate of high carbon steel or structural silicon steel, the metal at the point of cutting attains a very high temperature which drops very rapidly at the moment the cutting flame leaves each successive 'point. This rapid temperature drop is due to the chilling or quenching effect of the adjacent'air and the adjoining mass of metal,

and results in decided and objectionable changes in the physical properties of the metal along the cut or exposed surfaces, as set forth above.

Generally speaking, the objects of the invention are attained by what may be termed -localized heat treatment applied directly to such flame out surfaces and the metal adjoining the same, as by the localized application of oneor' more relatively small high-temperature oxy-fuel gas 5 flames. I

According to the present invention one or more oxy-acetylene or similar high temperature heating flames are progressively applied to suecessive portions of the edge or surface exposed and 0 thermally affected by the high-temperature cutting operation after the cut has been completed and before or after such edge or surface is completely cooled. Such localized high temperatureheating flame or flames are of sufficient number and intensity to heat the cut surface toa predetermined .degree; e. g., above the critical temperature of the metal being treated. Immediately following these reheating flames, a

suitable means forretarding the cooling rate of 40 the metal or even reheating it somewhat may be applied to the reheated edge. This means may be a source of less intense heat than is used. in the reheating step previously described, and preferably consists of one or more high temperature oxy-fuel gas flames applied to the reheated cut edge, the said gas flames being so regulated that the reheated edge will be cooled at sucha slow rate that the metallurgical structure of the edge portion of the metal will be so restored substantially to the initial metallurgical condition of the body of the metal. The cooling of the reheated surface is thus retarded sufflciently to anneal the metal; that is to say, the

metal, having been reheated above its critical temperature, has additional localized heat applied thereto whereby it is permitted to cool at such a slow rate as will result in a desirable 17, 1939. It is preferred to employ two or more .a desired maximum temperature.

separate multipie-nozzle oxy-acetyleneblowpipes A and B to perform the surface reconditioning operation along the hardened edges of flame-cut steel, as represented by the work-piece W. The blowpipes A and B are suitably mounted on a support S which may be adjusted vertically and horizontally with respect to the work W and which is movable lengthwise of the edge of the work so that the jets from the blowpipes may be made to traverse the entire cut surface ll of the work.

The blowpipe A is arranged so that the multiple nozzles will reheat the cut surface of the metal to By adapting the blowpipe B to confront a, relatively long area of the edge ofthe metahthe nozzles of this blowpipe may likewise be made to apply heat directly and substantially normally to the surface in such measure as to gradually retard the cooling process. The blowpipe B may be followed by means, such'as a forced draft of either hot or cold air, or other gases, or a jet of liquid, to suddenly cool or quench the surface at any predetermined temperature and thus produce a desired metallographic structure.

For the purpose of moving'the support S the blowpipes A and B relatively to the work, the

support S may be mounted on a carriage E which is adapted to roll on rails I2 adjacent and extending lengthwise of the edge of the work-piece W. The support S desirably comprises a yoke l3 having a rack 14, and a base l5 within which the yoke l3 may slide vertically when the rack is moved by a pinion l6 and'a hand operated wheel H. The base I5 is dovetailed to fit and rest on a slide l8, on which the entire support 5, is movable transversely of the carriage E by a handwheel and screw I9. When the work-piece W is resting on an elevated support or tablealongside of the rails l2, as in general practice, the blowpipes A and B may. be adjusted verticallyand spaced horizontally by the devices I! and 119,

. respectively, so as to properly position the blowpipes to operate on the work edge ,I I. The'carriage E may be propelled along the rails by a motor M and driving gearing20, and a rheostat 2| may be provided to control the amount of current passing through the motor fieldwi nd- ;ing and thus regulate the motorspeed and the rate of movement of the carriage E and the blow- ..pipes thereon with respect tothe workrpiece W.

In. accordance with this invention theinetal along the edge I.l isfirst reheated or raised to a predetermined degree above the critical ,tem-

.perature of the metal being treated, after'which thereheated edge is slowly cooled to restore {the properties ithad before being exposed liand thermally affected by the oxy -ffuel, as. flame, suchv as is used in a flame-cutting operation.

and

The reheating blowpipe A supplies the intense heat necessary to raise the temperature to the desired degree while the after-heating blowpipe B supplies less intense heat and is capable of, insuring gradual cooling in such a manner In the apparatus here shown, to this end the.

movement of the work and the blowpipes relatively to each other may be varied, as by increasing or decreasing themotor speed as the reheated condition of the cut edge varies from a predetermined standard. The operator of the apparatus may watch the reheating flame and the color of the reheated surface immediately after it leaves'the reheating flame, and may operate the rheostat 2| to increase or decrease the motor speed, as required to maintain the correct reheating condition. Obviously, such manual control may not be just right at every point, because the operator's judgment and skill may vary.

The correct reheating condition may be more exactly provided and maintained at every point along the surface II by mechanism which is automatically responsive 'to variations, from a predetermined standard, in the thermal condition or in the radiant energy emittedby the reheated surface. As shown in Fig. 1 of the drawing, this result may be accomplished by means of a photoelectric cell C which is focused on the reheated surface immediately behind the re-' heating blowpipe and is connected by an appropriate electrical circuit to a reversible electric motor 22 that is arranged to operate the rheostat 2| to increase or decrease the resistance in the circuit of the driving motor M and thereby vary termined reheating condition (determined by the proper initial setting of the'reheating flames and the feeding speed of motor M- when the reconditioning operation is started), there is a corresponding-change in gigs] "photocell circuit 23.

crease is amplified'in the amplifier 24 and transmitted to a coii25 which'a'ctuates a-contactor 26 to close the circuit of one or the' other of two relays 21 and 28 whichcontrol thesupply of current flowing in the s current increase or de-.

current from theline L tothe motor 22 and cause the latter and'the worm gearing 29 to rotate either clockwise or counterclockwise and thus operate the rheostat 2| to either increase or decrease the driving speed of motor M as re- .quired to instantaneously provide thep roper reheating condition at everypoint along (the sur-v face H. Accordingly,- with the photocell C fo-.

.-cused onv a narrow area of. theedge I I between thejblowpipes A. and B, and withthe electrical circuitssoadjusted that a predetermined and correct reheating condition is provided at start-- ing, it will be evident that the photocell "control Qsyste n will provide or maintain such predetermined reheated condition at successive points along the surface II as the reconditioning operation progresses. The blowpipes A and B may be provided with separate pairs of connections and valves 30 and 31 in order that suitable gases, such as oxygen and acetylene, may be delivered from supply conduits 32 and 33, respectively, at a lower pressure to the after-heating blowpipe B than to the reheating blowpipe A. The temperature produced by the jets of the after-heating blowpipe may be regulated within substantially wide limits to produce the required afterheating and the desired rate of slow cooling. An alternative type of blowpipe B, as shown in Fig. '4, may comprise a series of nozzles 4i] graduated from. nozzles of relatively great length adjacent the cell to short nozzles at the point at which the final-measure or increment of heat is applied to the work. With this arrangement of nozzles the heat delivered by the blowpipe B may be tapered off in intensity so that gradual cooling occurs along the edge of the metal. By either of the methods of controlling the application of heat from thejquenching blowpipe, it is possible to remove the source of heat when the temperature has been lowered to any predetermined degree. This'may be accomplished by blanking ofi nozzles at'gthe end of the blowpipe or by any other convenient method. It will be appreciated therefore that the steel may be softenedsoasto produce any desired grain structure by the manner of regulating the length of application and degree of heat of the quenching jets. In some instances it may be desirable to suddenly quench the cut surface after it has been reheated and subsequently cooled to a predetermined temperature. For this purpose quenching means, such as a jet of air or water, may be mounted on the support S in a position to closely follow the blowpipe B.

While it is preferable to employ gaseous heating means to recondition flame-cut metal surfaces; it will be evident that electrical heating means such as electric arcs may be used in some instances to reheat such surfaces or retard their cooling, or a combination of the gaseous and electrical heating media may be used, one for reheating and the other for retarding cooling. While the herein-disclosed invention is especially applicable to the reconditioning of air-hardening grades of structural steel, it is obvious that the principles of this invention may also be employed in treating and reconditioning surfacesof other metals which have been exposed and thermally affected by an oxy-acetylene cutting flame or an equivalent high-temperature severing procedure. Various other changes may be made in the details of the method herein disclosed without departing from the invention or sacrificing any of its important advantages.

We claim:

1. A method of reconditioning the metallurgical structure of metal, which comprises progressively applying a first source of intense heat locally to the surface to be reconditioned, and retarding the cooling of the intensely heated portions of said surface by progressively applying a second source of less intense heat locally to the successive heated portions of said surface.

2. A method of reconditioning the metallurgical structure of metal cut by the action thereon of oxidizing and high-temperature heating agents, which comprises progressively applying a high-temperature heating flame locally to the surface exposed and thermally affected by the cutting operation, and applying additional heat of less intensity than said flame to the successive reheated portions of said surface to retard the cooling thereof.

3. A method of substantially eliminating objectionable change produced in the metallurgical structure of high carbon steels, structural silicon steels and other alloy steels when out by the action thereon of oxidizing and high-temperature heating agents, said method comprising progressively applying high-temperature reheating flames locally to the surface exposed and thermally affected by the cutting operation to reheat successive portions of said surface; continuously regulating the reheating operation in accordance with the thermal condition of said surface as it becomes reheated; and progressively and locally applying, to the reheated areas of said surface, flames of less intensity than the reheating flames, to retard the normal cooling of such surface portions.

HERBERT H. MOSS.

JOSEPH R. DAWSON. 

